You can make such an argument in two possible ways.
First, you can argue that it was necessary from a practical point of view. The war was badly hurting Britain, with which the United States had a great deal of trade. It was necessary for the US to enter the war in order to protect its trade with Great Britain and to ensure that its ally and trading partner would not suffer further in the war.
Second, you can argue that it was necessary from a moral/ethical point of view. You can argue that it was necessary to prevent Germany from continuing to violate international law. You can argue that it was necessary in order to preserve the rights of neutral nations to enjoy the freedom of the seas.
In this way, it can be argued both from a pragmatic and an ethical point of view that the US needed to enter WWI.